Method and equipment for performing continuous extrusion

ABSTRACT

The invention relates to a method for performing continuous extrusion of a metallic material, such as copper, so that the material to be extruded ( 1 ) is fed in the extrusion member ( 4 ) by means of a feed member ( 3 ) provided with a groove on its peripheral wall ( 2 ) and by an abutment ( 5 ) arranged in said groove, so that the groove ( 8 ) is protected against oxidation by arranging for at least part of the peripheral wall ( 2 ) of the feed member ( 3 ) a gas-protecting member ( 7 ). The invention also relates to said equipment.

The invention relates to a method and equipment according to theindependent claims for performing continuous extrusion of a metallicmaterial, such as copper.

In continuous extrusion, the material to be extruded is conducted in agroove made on the outer circumference of a wheel-like element. As theelement rotates around its axis, the material to be extruded gets intocontact with an abutment that essentially fills the groove, so that themotion of the material to be extruded is changed with respect to thewheel-like member. Thus the material is arranged to be extruded in theproceeding direction of the material before the abutment, through apassageway arranged in the extrusion member. The method utilizesfriction and thermal energy created in the working process. By means ofthe method, it is possible to advantageously extrude essentially longobjects that are different in their transversal surfaces.

In the course of the process, it is possible that on the surface ofobjects made of copper or copper alloys, there are created oxide layersthat are harmful in the further processing of said objects. Intraditional extrusion, in the vicinity of the surface there may becreated oxide layers that result in the tearing of the structure inhydrogen annealing. When welding thin strips into tubes, oxides maycreate leakages in the welding area. Surfaces must be cleaned severaltimes of the oxide layers accumulated thereon. Oxide layers aredifficult to detect or measure on the surface of copper, and they arenot necessarily distinguished without special equipment. The removal ofthick oxide layers from the surface of copper is fairly simple, but theremoval of the last molecular layers has turned out to be moredifficult.

In traditional continuous extrusion, oxides are removed as so-calledextrusion scrap, the processing and recirculation of which bring forthdisadvantageous extra expenses. In addition, the creation of hotextrusion scrap results in an intensive wearing of the extrusion tools.Even if oxides were removed from the surface of the feed material beforethe continuous extrusion, oxidation could also take place during theextrusion of the material. When manufacturing a copper product byextrusion, a completely oxygen-free process would ensure a betterquality for the product. It is well-known that in order to solve saidproblem, the extrusion equipment is protected by surrounding theequipment by an atmosphere that prevents the passage of oxides and otherimpurities in the extruded product. However, it has been found out thateven slight oxygen-contents in the protecting gas may cause oxidationthat is harmful for the product. Also the groove lining may be oxidizedowing to a too high oxygen level in the gas protection, which may causeoccasional flaws in the products.

In the patent publication U.S. Pat. No. 5,782,120, there is described anequipment for continuous extrusion, where the feed member, i.e. a wheel,included in the extrusion equipment is protected by a hood containingnon-oxidizing gas.

The object of the present invention is to introduce a novel solution forperforming continuous extrusion of a material. A particular object ofthe invention is to introduce a solution where the product created incontinuous extrusion is protected against oxidation.

The invention is characterized by what is set forth in thecharacterizing parts of the independent claims. Other preferredembodiments of the invention are characterized by what is set forth inthe other claims.

Remarkable advantages are achieved by the arrangement according to theinvention. The invention relates to a method for performing continuousextrusion of a metallic material, such as copper, so that the materialto be extruded is fed in the extrusion member by means of a feed memberprovided with a groove on its peripheral wall and an abutment arrangedin the groove; the groove is protected against oxidation by providing atleast part of the peripheral wall of the feed member with agas-protecting member. The gas-protecting member according to theinvention advantageously enables the feeding of non-oxidizing gases inthe groove area, which in turn prevents the passage of oxygen and oxidesin the extrusion product. The gas-protecting member according to theinvention is arranged at least on that part of the peripheral wall thatdoes not contain material to be extruded, and the gas-protecting membercovers at least part of the surface of the peripheral wall of the feedmember in the width direction thereof. Thus the oxidation of the grooveis particularly prevented at the hottest spot of the feed member, on theperipheral wall of the feed member after the abutment, where thematerial to be extruded is removed from the groove. The hot surface ofthe groove lining is a remarkable source of oxides and consequentlyenhances the oxidation of the product. According to the invention, thegas-protecting member is arranged on the peripheral wall of the feedmember, so that it covers at least the groove, in which case the spaceleft between the gas-protecting member and the feed member is arrangedto be oxygen-free. In the space left between the gas-protecting memberand the feed member, there is fed non-oxidizing gas, such as hydrogen orhydrogen and nitrogen, by means of the gas-protecting member. The gascan be preheated up to for example 400-800 degrees. According to apreferred embodiment of the invention, oxygen is removed from the gas tobe fed in prior to feeding it in the space left between thegas-protecting member and the feed member. Oxygen can be removed byusing prior art methods, such as filtering. Thus even extremely lowoxygen contents can be eliminated. Hydrogen can advantageously be usedfor removing oxygen from neutral gases. Nitrogen is fed in forcirculation-technical reasons. According to the invention, the extrusionprocess is surrounded by an inert gas protection, and the effects of theresidual oxygen contained by said gas protection are eliminated byapplying the solution of the invention. In the space left between thegas-protecting member and the feed member, i.e. in the vicinity of thegroove, there prevails a higher pressure than in the inert gasprotection, and the gas circulation is thus directed away from thegroove.

The invention also relates to an equipment for performing continuousextrusion of metallic material, such as copper, so that the material tobe extruded is fed in the extrusion member by means of a feed memberprovided with a groove on its peripheral wall and an abutment arrangedin the groove, so that at least part of the peripheral wall of the feedmember is provided with a gas-protecting member for protecting thegroove against oxidation.

According to a preferred embodiment of the invention, the gas-protectingmember comprises at least one protecting member provided with at leastone gas channel for feeding gas into the space left between thegas-protecting member and the feed member. Thus the gas can beconducted, through the gas-protecting member, in a desired spot in thegroove. According to an embodiment of the invention, the gas-protectingmember comprises an inner protecting member and at least one outerprotecting member. According to the invention, the gas fed in from theinner protecting member has a higher pressure than the gas fed in fromthe outer protecting member. There is thus created a circulation awayfrom the groove through the gap left between the protection member andthe feed member. On both sides of the groove, on the peripheral wall ofthe feed member, there is provided at least one lining element forsealing the gap between the gas-protecting member and the feed member.The lining element is made of the same material as the material to beextruded. Thus the residual oxygen from the gas protection surroundingthe whole extrusion equipment is advantageously prevented from accessingthe vicinity of the groove.

The solution according to the invention enables the creation of anoxygen-free space in the groove vicinity, which enhances themanufacturing of a flawless extrusion product. Consequently, thedrawbacks caused by the processing and recirculation of extrusion scrapare avoided, because the creation of extrusion scrap is prevented.

The invention is described in more detail below with reference to theappended drawings.

FIG. 1 An equipment according to the invention

FIG. 2 An equipment according to the invention

FIG. 3 An equipment according to the invention

FIG. 1 illustrates how, according to the invention, the material to beextruded 1, such as copper wire, is fed in the groove 8 located on theperipheral wall 2 of the feed member 3 by means of a pressure roller 18.The feed member 3 rotates around its axis, and the material to beextruded moves along the groove to the extrusion member 4 to beextruded. In connection with the extrusion, the temperature of thematerial to be extruded rises owing to the friction forces up to thetemperature range of 550-750 degrees. In order to direct the material tobe extruded to the extrusion member 4, the groove of the feed member isprovided with an abutment 5 that extends over part of the length of thewheel groove. In the extrusion member 4, there is made a passageway of adesired shape, and the extrusion product is conducted out of the feedmember 3 through said passageway. The extrusion process is throughoutprotected by a protective gas 6 against external room air. In thedrawing, there is distinguished the gas-protecting member 7 arranged onpart of the peripheral wall.

FIGS. 2 and 3 show how the gas-protecting member 7 according to theinvention is arranged in the vicinity of the groove 8. FIGS. 2 and 3 arecross-sectional views of FIG. 1, seen along the line A - A. According tothe invention, for at least part of the peripheral wall 2 of the feedmember, there is arranged a gas-protecting member 7 in order to protectthe groove against oxidation. According to the example of the invention,the gas-protecting member is arranged on that part of the peripheralwall 2 that does not contain material to be extruded. By means of thegas-protecting member 7, the vicinity of the groove 8 of the feed member3 is set in an oxygen-free atmosphere, which enhances the creation of aflawless and high-quality extrusion product. The gas-protecting member 7is made of some wear-resistant material, such as steel, and in shape, itmay conform for example to the peripheral wall 2 of the feed member 3.The gas-protecting member covers at least part of the surface of theperipheral wall 2 in the width direction, and at least it covers thegroove 8. According to the invention, the space 9 left between thegas-protecting member and the feed member is arranged to be oxygen-freeby feeding in a desired amount of non-oxidizing gas. According to theinvention, in the space 9 there is fed a gas mixture, heated up to thetemperature of 600 degrees and containing hydrogen and nitrogen. Thenon-oxidizing gas can be removed through a specially arranged removalroute.

The gas-protecting member 7 according to the example, illustrated inFIG. 2, includes a protecting member 10 provided with at least one gaschannel 11, through which gas can be fed into the space 9 left betweenthe feed member 3 and the gas-protecting member. When necessary, the gaschannel can extend along the whole length of the gas-protecting member7, or only along part of its length. Gas can be fed in at desired spotsin the groove 9. The groove is provided with a lining 12 that protectsthe groove from wearing. Advantageously the lining is made of the samematerial as the material to be extruded, such as copper. In between thegas-protecting member and the feed member, on both sides of the groove,there are arranged lining elements 13 in order to seal the gap 17between the gas-protecting member and the feed member.

FIG. 3 illustrates an embodiment of the invention, according to whichthe gas-protecting member 7 comprises an inner protecting member 10 andat least one outer protecting member 14. The outer protecting memberincludes at least one gas channel 15, through which non-oxidizing gascan be fed. The gas fed in through the inner protecting member 10 has ahigher pressure than the gas fed in through the outer protecting member14. Thus the gas space 16 left between the outer protecting member 14and the inner protecting member 10 has a lower pressure than the space 9left between the inner protecting member and the feed member.Consequently, the gas is made to flow in the desired direction, awayfrom the groove. In addition, on both sides of the groove, on theperipheral wall 2 of the feed member 3, there are arranged liningelements 13, essentially so that they seal the gap 17 left between thegas-protecting member and the feed member, however so that gas can flowout of the groove 8.

For a man skilled in the art, it is obvious that the various preferredembodiments of the invention are not restricted to the examplesdescribed above, but may vary within the scope of the appended claims.

1. A method for performing continuous extrusion of a metallic material,comprising feeding a metallic material into a groove located on aperipheral wall of a feed member, wherein the groove has an abutmentarranged in said groove, protecting the groove against oxidation by agas-protecting member for at least part of the peripheral wall of thefeed member, wherein pressure in a space left between the gas-protectingmember and the feed member is higher than the pressure in thesurrounding atmosphere, and moving the metallic material along thegroove into an extrusion member.
 2. The method according to claim 1,wherein the gas-protecting member is arranged at least in a part of theperipheral wall that does not contain material to be extruded.
 3. Themethod according to claim 1, wherein the gas-protecting member covers atleast part of the surface of the peripheral wall of the feed member inthe direction of the width thereof.
 4. The method according to claim 1,wherein the gas-protecting member covers at least the groove.
 5. Themethod according to claim 1, comprising feeding non-oxidizing gasthrough the gas-protecting member into the space left between thegas-protecting member and the feed member.
 6. The method according toclaim 5, feeding hydrogen into the space left between the gas-protectingmember and the feed member.
 7. The method according to claim 5,comprising feeding hydrogen and nitrogen into the space left between thegas-protecting member and the feed member.
 8. The method according toclaim 5, comprising preheating the non-oxidizing gas up to 400-800degrees.
 9. The method according to claim 5, removing oxygen from thenon-oxidizing gas by filtration before feeding the gas into the spaceleft between the gas-protecting member and the feed member.
 10. Themethod according to claim 1, protecting the extrusion method with aninert gas.
 11. The method according to claim 10, wherein the pressure inthe space left between the gas-protecting member and the feed member ishigher than the pressure in the inert gas.
 12. Equipment for performingcontinuous extrusion of a metallic material, comprising a groove locatedon a peripheral wall of a feed member; an abutment arranged in saidgroove; and for at least part of the peripheral wall of the feed member,a gas-protecting member, wherein pressure in a space left between thegas-protecting member and the feed member is higher than the pressure inthe surrounding atmosphere.
 13. The equipment according to claim 12,wherein the gas-protecting member comprises at least one protectingmember provided with at least one gas channel for feeding gas into thespace left between the gas-protecting member and the feed member. 14.The equipment according to claim 13, wherein the gas-protecting membercomprises an inner protecting member and at least one outer protectingmember.
 15. The equipment according to claim 14, wherein the gas fedthrough the inner protecting member has a higher pressure than the gasfed in through the outer protecting member.
 16. The equipment accordingto claim 12, comprising at least one lining element on both sides of thegroove, on the peripheral wall of the feed member in order to seal a gapleft between the gas-protecting member and the feed member.
 17. Theequipment according to claim 16, wherein the lining element is made ofthe same material as the metallic material to be extruded.
 18. Theequipment according to claim 12, wherein the metallic material iscopper.
 19. The method according to claim 1, wherein the metallicmaterial is copper.